Treatments for food allergy: how close are we?

A mouse model of food allergy permitting skin and nasal symptoms

PURPOSE

Developing experimental animal models that show clinical symptoms and methods for quantitative and objective evaluation are important for understanding food allergies. Therefore, this study aimed to develop an ovalbumin (OVA)-induced mouse model of food allergy and a useful method to evaluate the symptoms of food allergy.

MATERIAL/METHODS

Mice were sensitized via intraperitoneal injection of OVA. Subsequently, local sensitization was performed once weekly by oral administration of OVA. Itching and nasal symptoms were observed after oral administration of the antigen. First, we examined the dose-dependency of the antigen. Symptoms were checked weekly. In order to confirm food allergy symptoms, the effect of histamine H1 receptor antagonist was examined. Finally, we measured antigen-specific IgE antibody levels in the serum.

RESULTS

Scratching behavior, sneezing and nasal rubbing were increased. Both itching and rhinitis symptoms increased steadily, after which, the number of symptoms remained almost constant. No difference was observed between the results of 3- and 5-week-old mice. Cetirizine inhibited these symptoms in a dose-dependent manner. In addition, antigen-specific IgE antibodies were produced in both 3- and 5-week-old mice.

CONCLUSIONS

This method may be useful for evaluating the symptoms of skin and rhinitis that could not be assessed in the conventional food allergy model and could be induced with a low dose of antigen. In particular, the developed method, which measures the number of itching and nasal symptoms, may enable quantitative, objective, and noninvasive evaluation of food allergy severity.

Folding-Based Electrochemical Aptasensor for the Determination of β-Lactoglobulin on Poly-L-Lysine Modified Graphite Electrodes

Nowadays, food allergy is a very important health issue, causing adverse reactions of the immune system when exposed to different allergens present in food. Because of this, the development of point-of-use devices using miniaturized, user-friendly, and low-cost instrumentation has become of outstanding importance. According to this, electrochemical aptasensors have been demonstrated as useful tools to quantify a broad variety of targets. In this work, we develop a simple methodology for the determination of β-lactoglobulin (β-LG) in food samples using a folding-based electrochemical aptasensor built on poly-L-lysine modified graphite screen-printed electrodes (GSPEs) and an anti-β-lactoglobulin aptamer tagged with methylene blue (MB). This aptamer changes its conformation when the sample contains β-LG, and due to this, the spacing between MB and the electrode surface (and therefore the electron transfer efficiency) also changes. The response of this biosensor was linear for concentrations of β-LG within the range 0.1-10 ng·mL-1, with a limit of detection of 0.09 ng·mL-1. The biosensor was satisfactorily employed for the determination of spiked β-LG in real food samples.

Recent progress on cell-based biosensors for analysis of food safety and quality control

Food quality and safety has become a subject of major concern for authorities and professionals in the food supply chain. Rapid methods, particularly biosensors, have exceptional specificity and sensitivity, rapid response times, low cost, relatively compact size, and are user friendly to operate. Cell-based biosensors are portable, and provide the biological activity of the analyte suitable for an initial screening of food. In this overview, the utilization of cell-based biosensors for food safety and quality analyses, such as detecting toxins, foodborne pathogens, allergens, and evaluating toxicity and function are summarized. Our results will promote the future development of cell-based biosensors in the food field.

IL-33 promotes gastrointestinal allergy in a TSLP-independent manner

Atopic dermatitis (AD) often precedes asthma and food allergy, indicating that epicutaneous sensitization to allergens may be important in the induction of allergic responses at other barrier surfaces. Thymic stromal lymphopoietin (TSLP) and interleukin (IL)-33 are two cytokines that may drive type 2 responses in the skin; both are potential targets in the treatment of allergic diseases. We tested the functional role of IL-33 and the interplay between IL-33 and TSLP in mouse models of atopic march and gastrointestinal (GI) allergy. IL-33-driven allergic disease occurred in a TSLP-independent manner. In contrast, mice lacking IL-33 signaling were protected from onset of allergic diarrhea in TSLP-driven disease. Epithelial-derived IL-33 was important in this model, as specific loss of IL-33 expression in the epithelium attenuated cutaneous inflammation. Notably, the development of diarrhea following sensitization with TLSP plus antigen was ameliorated even when IL-33 was blocked after sensitization. Thus, IL-33 has an important role during early cutaneous inflammation and during challenge. These data reveal critical roles for IL-33 in the "atopic march" that leads from AD to GI allergy.

Allergenicity Assessment of Transgenic Wheat Lines In Silico

Agriculture biotechnology is a promising tool for developing varieties with enhanced quality and quantity. Transgenic proteins expressed by genetically modified (GM) food crops improve crop characteristics like nutritional value, taste, and texture, and endow plants with resistance against fungus, pests, and insects. Despite such potential benefits, there are concerns regarding possible adverse effects of GM crops on human health, animals and the environment. Among the proposed guidelines for GM food safety testing-the weight-of-evidence approach proposed by the Codex Alimentarius Commission (ALINORM 03/34A) is the most recent. Till date, several transgenic wheat lines have been developed and research is underway for further improvement. However, GM wheat is not being grown or consumed in any part of the world. In the present study, in silico tools were employed for safety testing of eight transgenes used for the development of transgenic wheat lines. Among the genes studied, none of them shared sequence homology with the reported allergens and may be safe for use in genetic engineering. In conclusion, gene selection for developing transgenic wheat lines should be done with utmost care to ensure its safety for feed and fodder.

Immunotherapy using algal-produced Ara h 1 core domain suppresses peanut allergy in mice

Peanut allergy is an IgE-mediated adverse reaction to a subset of proteins found in peanuts. Immunotherapy aims to desensitize allergic patients through repeated and escalating exposures for several months to years using extracts or flours. The complex mix of proteins and variability between preparations complicates immunotherapy studies. Moreover, peanut immunotherapy is associated with frequent negative side effects and patients are often at risk of allergic reactions once immunotherapy is discontinued. Allergen-specific approaches using recombinant proteins are an attractive alternative because they allow more precise dosing and the opportunity to engineer proteins with improved safety profiles. We tested whether Ara h 1 and Ara h 2, two major peanut allergens, could be produced using chloroplast of the unicellular eukaryotic alga, Chlamydomonas reinhardtii. C. reinhardtii is novel host for producing allergens that is genetically tractable, inexpensive and easy to grow, and is able to produce more complex proteins than bacterial hosts. Compared to the native proteins, algal-produced Ara h 1 core domain and Ara h 2 have a reduced affinity for IgE from peanut-allergic patients. We further found that immunotherapy using algal-produced Ara h 1 core domain confers protection from peanut-induced anaphylaxis in a murine model of peanut allergy.

Peanut T-cell epitope discovery: Ara h 1

BACKGROUND

Identification of potential T-cell epitopes in the peanut major allergens is essential for development of peptide-based immunotherapy. Traditional methods of T-cell epitope discovery use overlapping short peptides spanning the full length of the protein in T-cell proliferation assays. Because large proteins, such as Ara h 1, require a large number of peptides, this limits screening to a small number of allergic subject-derived T-cell lines.

OBJECTIVE

We sought to identify candidate peptides of Ara h 1 that display promiscuous binding to MHC class II and induce TH2 cytokine production by T cells.

METHODS

In silico MHC class II binding prediction was performed with NetMHCIIpan 2.0 (peptide length, 15; 1-mer offset) and the most abundant class II alleles in the North American population and with an in vitro MHC class II peptide reporter assay performed in parallel, which used synthetic 15-mer peptides offset by 5 mer spanning the protein. High-resolution MHC class II typing and a T-cell proliferation assay using preselected peptides were performed with PBMCs from 98 subjects with peanut allergy and 14 healthy control subjects. IL-4, IL-13, IL-5, IFN-γ, and TNF-α levels were measured in culture supernatants.

RESULTS

Thirty-six Ara h 1 peptides were identified by using in silico predictions and MHC class II binding assays. In combination with T-cell proliferation and cytokines secreted in T-cell assays, we have identified 4 vaccine candidate Ara h 1 peptides.

CONCLUSIONS

Preselection of peptides by using in silico and in vitro approaches in combination with conventional methods appears to be an effective strategy for identifying peanut T-cell peptide vaccine candidates.

Immunotherapy with B cell epitopes ameliorates inflammatory responses in Balb/c mice

Osmotin, a protein from the pathogenesis-related family (PR-5), has been identified as an allergen based on in-silico and in-vitro studies. In the present study, three B cell epitopes of osmotin with single and double amino acid modifications were studied for immunotherapy in a murine model. The single-modification peptides (P-1-1, P-2-1 and P-3-1) and double-modification peptides (P-1-2, P-2-2 and P-3-2) showed significantly lower immunoglobulin (Ig)E binding with patients' sera compared to osmotin (P < 0·01). These peptides showed reduced IgE binding compared to the unmodified peptides (B cell epitopes) P-1, P-2 and P-3. Among the modified peptides, P-2-1, P-3-1, P-2-2 and P-3-2 showed significant reduction in IgE binding and were used for immunotherapy in mice. The sera of mice group treated with peptides showed a significant increase in IgG2a level and a significant decrease in IgE and IgG1 levels (P < 0·05). The mice that received peptide immunotherapy showed a shift from a T helper type 2 (Th2) to Th1 type where interferon (IFN)-γ and interleukin (IL)-10 levels were elevated, with a significant increase in groups treated with peptides P-3-1 and P-3-2 (P < 0·05). There was a reduction in the IL-4 and IL-5 levels in bronchoalveolar lavage fluid (BALF) in the peptide-treated mice groups. Total cell count and eosinophil count in BALF of the peptide-treated groups was also reduced compared to the phosphate-buffered saline (PBS)-treated group. Lung histology showed a significant reduction in cellular infiltrate in mice treated with P-2-2 and P-3-2 compared to PBS. In conclusion, peptides P-2-2 and P-3-2 lowered inflammatory responses and induced a Th1 response in mice.

Cardiac mMCP-4+ mast cell expansion and elevation of IL-6, and CCR1/3 and CXCR2 signaling chemokines in an adjuvant-free mouse model of tree nut allergy

BACKGROUND

Nut allergy is a growing and potentially fatal public health problem. We have previously reported a novel mouse model of near-fatal hazelnut (HN) allergy that involves transdermal sensitization followed by oral elicitation of allergic reactions. Here we studied the cardiac mast cell and cardiac tissue responses during oral nut induced allergic reaction in this mouse model.

METHODS

Groups of mice were sensitized with HN and specific and total IgE were measured by ELISA. Oral allergic reaction was quantified by rectal thermometry and plasma mouse mast cell protease (mMCP)-1 by ELISA. Cardiovascular functions were determined by a non-invasive tail cuff method. Mucosal mast cells (MMC) and intestinal connective tissue MC (CTMC) were studied by immunohistochemistry (IHC) for mMCP-1 and mMCP-4 protein expression respectively. Cardiac MC were studied by toluidine blue (TB) as well as by the above IHC methods. Cytokines and chemokines in the tissues were quantified by a multiplex protein array method.

RESULTS

Oral allergen challenge (OAC) of transdermal sensitized mice results in hypothermia, hypotension, tachycardia and rapid elevation of circulating mMCP-1. The IHC analysis of small intestine found significant expansion of mMCP-1+ MMCs and mMCP-4+ CTMCs. The TB analysis of cardiac tissues showed degranulation of majority of cardiac MCs. The IHC analysis of cardiac tissues showed very little mMCP-1 expression, but marked mMCP-4 expression. Furthermore, repeated OAC resulted in significant expansion of mMCP-4+ cardiac MCs in both the pericardium and the myocardium. Protein array analysis revealed significant elevation of cardiac IL-6 and CCR1/3 and CXCR2 signaling chemokines upon oral elicitation compared to sensitization alone.

CONCLUSION

These results demonstrate that: (i) besides the intestine, cardiac mast cells and the cardiac tissue respond during oral nut induced allergic reaction; and (ii) repeated oral elicitation of reaction is associated with cardiac mMCP-4+ mast cell expansion and elevation of cardiac IL-6, and CCR1/3 and CXCR2 signaling chemokines.

Exposure to food allergens through inflamed skin promotes intestinal food allergy through the thymic stromal lymphopoietin-basophil axis

BACKGROUND

Exposure to food allergens through a disrupted skin barrier has been recognized as a potential factor in the increasing prevalence of food allergy.

OBJECTIVE

We sought to test the immunologic mechanisms by which epicutaneous sensitization to food allergens predisposes to intestinal food allergy.

METHODS

Mice were epicutaneously sensitized with ovalbumin or peanut on an atopic dermatitis-like skin lesion, followed by intragastric antigen challenge. Antigen-specific serum IgE levels and T(H)2 cytokine responses were measured by ELISA. Expression of type 2 cytokines and mast cell proteases in the intestine were measured by using real-time PCR. Accumulation of basophils in the skin and mast cells in the intestine was examined by using flow cytometry. In vivo basophil depletion was achieved by using diphtheria toxin treatment of Baso-DTR mice. For cell-transfer studies, the basophil population was expanded in vivo by means of hydrodynamic tail vein injection of thymic stromal lymphopoietin (TSLP) cDNA plasmid.

RESULTS

Sensitization to food allergens through an atopic dermatitis-like skin lesion is associated with an expansion of TSLP-elicited basophils in the skin that promote antigen-specific T(H)2 cytokine responses, increased antigen-specific serum IgE levels, and accumulation of mast cells in the intestine, promoting the development of intestinal food allergy. Critically, disruption of TSLP responses or depletion of basophils reduced the susceptibility to intestinal food allergy, whereas transfer of TSLP-elicited basophils into intact skin promoted disease.

CONCLUSION

Epicutaneous sensitization on a disrupted skin barrier is associated with accumulation of TSLP-elicited basophils, which are necessary and sufficient to promote antigen-induced intestinal food allergy.

Matrix-normalised quantification of species by threshold-calibrated competitive real-time PCR: allergenic peanut in food as one example

A novel method to quantify species or DNA on the basis of a competitive quantitative real-time polymerase chain reaction (cqPCR) was developed. Potentially allergenic peanut in food served as one example. Based on an internal competitive DNA sequence for normalisation of DNA extraction and amplification, the cqPCR was threshold-calibrated against 100mg/kg incurred peanut in milk chocolate. No external standards were necessary. The competitive molecule successfully served as calibrator for quantification, matrix normalisation, and inhibition control. Although designed for verification of a virtual threshold of 100mg/kg, the method allowed quantification of 10-1,000 mg/kg peanut incurred in various food matrices and without further matrix adaption: On the basis of four PCR replicates per sample, mean recovery of 10-1,000 mg/kg peanut in chocolate, vanilla ice cream, cookie dough, cookie, and muesli was 87% (range: 39-147%) in comparison to 199% (range: 114-237%) by three commercial ELISA kits.

A murine monoclonal antibody based enzyme-linked immunosorbent assay for almond (Prunus dulcis L.) detection

A sandwich enzyme-linked immunosorbent assay (ELISA) using anti-almond soluble protein rabbit polyclonal antibodies as capture antibodies and murine monoclonal antibody 4C10 as the detection antibodies was developed. The assay is specific and sensitive (3-200 ng almond protein/mL) for almond detection. The standardized assay is accurate (<15% CV) and reproducible (intra- and inter assay variability <15% CV). The assay did not register any cross-reactivity with the tested food matrices, suggesting the assay to be almond amandin specific. The assay could detect the presence of declared almond in the tested matched commercial samples. Further, the assay reliably detected the presence of almonds in the laboratory prepared food samples spiked with almond flour.

Identification of rice proteins recognized by the IgE antibodies of patients with food allergies

Similarity among food allergens is a great problem affecting the specificity of diagnosis and treatment of allergic patients. We have observed that 80% of patients with food (including wheat) and pollen allergies have increased IgE antibodies against rice proteins. By immunoblotting, we documented that boiling decreased solubility and IgE reactivity of PBS-extracted rice and wheat proteins, yet in SDS extracts this reactivity was only slightly changed. The sera of patients highly positive on the IgE immunoblot and positive in basophil activation and skin prick test with boiled rice components were used for characterizing the IgE-binding proteins separated by 1D or 2D electrophoresis. Using mass spectrometry, we identified 22 rice SDS soluble proteins. Six of them were new thermostable potential rice allergens: glutelin C precursor, granule-bound starch synthase 1 protein, disulfide isomerase-like 1-1 protein, hypothetical protein OsI_13867, putative acid phosphatase precursor 1, and a protein encoded by locus Os02g0453600. All of the identified rice proteins differed from known wheat allergens, except proteins belonging to the α-amylase/trypsin inhibitor family. Furthermore, we would suggest that in patients with high IgE reactivity to wheat and rice components, the IgE immunoblot and skin prick test with boiled rice proteins could be beneficial before diet recommendation.